An architecture where more than one layer communicates with the base layer.  The latter is not necessarily the least abstraction layer.

One example is Logical Volume Groups, http://www.tldp.org/HOWTO/LVM-HOWTO/anatomy.html, where a volume group comprises physical volumes yet presents logical volumes.  The volume group is the base.

The name for this kind of architecture is not known to the person who posted this article.  Anyone having an appropriate term is welcome to replace it here.


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I'm not sure the statement here is true, but let me know if I'm wrong. 

A volume group is a group of physical volumes e.g. a bunch of extents on any number of physical disks. Used to provide mirroring or striping or aggregated lumps of disk. It presents itself as a virtual physical volume, or in unix terms, a device.

Then you've got logical volumes which split the physical volume (virtual or otherwise) into logical lumps of disk, often presented as devices which is probably a hangover from the unix approach to partitioning, with one partition per device.

Then you get directories which are the O/S filesystem abstraction, mounted onto devices.

So it is a simple hierarchy of abstraction.

Since each layer presents essentially the same interface, i.e. looks like a physical volume, it is not unusual for filesystems to mount at any layer. Perhaps that is what the page is looking to describe?

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